Corrosion inhibitor

Abstract

A composition, in contact with a corrodable metal surface, which composition comprises: (A) an aqueous-based or oil-based system; and (B) as inhibitor for protecting the metal surface against corrosion, a mixture comprising at least one compound of formula I and at least one compound of formula II: ##STR1## wherein R is a monoalkylglycol ether of formula II R.sub.3 [O(CH.sub.2).sub.m ].sub.p O(CH.sub.2).sub.m-1 -- III R 1 is H, CO 2 M or C 1 -C 4 straight or branched chain alkyl residue; R 2 is H, C 1 -C 4 straight or branched chain alkyl residue -CH 2 CO 2 M or -CH 2 CH 2 CO 2 M; R 3 is C 4 -C 20 straight or branched chain alkyl residue, C 6 -C 10 aryl residue (optionally substituted by C 1 -C 15 alkyl residues), C 5 -C 12 cycloalkyl residue, or a C 7 -C 12 aralkyl group optionally substituted by C 1 -C 15 alkyl residues; n is a number from 0 to 20 m is a number from 2 to 4 p is a number from 0 to 20; and M is a metal ion, H or an optionally substituted ammonium ion.

We claim: 
     
       1. A composition, in contact with a corrodable metal surface, which composition comprises: (A) an aqueous-based or oil-based system; and   (B) as inhibitor for protecting the metal surface against corrosion, a mixture comprising at least one compound of formula I and at least one compound of formula II: ##STR8##  wherein R is a monoalkylglycol ether group of formula III   R.sup.3 [O(CH.sub.2).sub.m ].sub.p O(CH.sub.2).sub.m-1 --  III     R 1  is H, CO 2  M or C 1  -C 4  straight or branched chain alkyl residue;   R 2  is H, C 1  -C 4  straight or branched chain alkyl residue, --CH 2  CO 2  M or --CH 2  CH 2  CO 2  M;   R 3  is C 4  -C 20  straight or branched chain alkyl residue, C 6  -C 10  aryl residue, C 6  -C 10  aryl residue substituted by C 1  -C 15  alkyl residues, C 5  -C 12  cycloalkyl residue, a C 7  -C 12  aralkyl group, or a C 7  -C 12  aralkyl group substituted by C 1  -C 15  alkyl residues;   n is a number from 0 to 20;   m is a number from 2 to 4;   p is a number from 0 to 20; and   M is a metal ion, hydrogen, an ammonium ion or a substituted ammonium ion.     
     
     
       2. A composition according to claim 1 wherein the corrodable metal surface is a ferrous metal surface. 
     
     
       3. A composition according to claim 1 wherein R 1  is H or CO 2  M. 
     
     
       4. A composition according to claim 1 wherein R 2  is H. 
     
     
       5. A composition according to claim 1 wherein R 3  is a C 8  -C 20  straight or branched chain alkyl residue. 
     
     
       6. A composition according to claim 1 wherein n is a number from 0 to 10. 
     
     
       7. A composition according to claim 1 wherein m is a number from 2 to 3. 
     
     
       8. A composition according to claim 1 wherein p is a number from 0 to 6. 
     
     
       9. A composition according to claim 1 wherein M is hydrogen, sodium, potassium or Ca/2. 
     
     
       10. A composition according to claim 1 wherein the total amount of the mixture of compound(s) of formula I and II ranges from 0.0001 to 5% by weight, based on the total weight of the aqueous- or oil-based system. 
     
     
       11. A composition according to claim 10 wherein the total amount of the mixture of compound(s) of formula I and II ranges from 0.01 to 5% by weight, based on the total weight of the aqueous- or oil-based system. 
     
     
       12. A composition according to claim 1 wherein the ratio of compounds I and II in the mixture (B) is in the range of from 100:1 to 0.01:1. 
     
     
       13. A composition according to claim 12 wherein the ratio of compounds I and II in the mixture (B) is in the range of from 10:1 to 0.1:1. 
     
     
       14. A composition according to claim 13 wherein the ratio of compounds I and II in the mixture (B) is in the range of from 1:1 to 0.1:1. 
     
     
       15. A composition according to claim 1 wherein the system is oil-based and the system also contains one or more antioxidants, metal deactivators, further corrosion or rust inhibitors, viscosity-index improvers, pour-point depressants, dispersants/surfactants or anti-wear additives. 
     
     
       16. A composition according to claim 1, wherein the system is aqueous-based and the system contains one or more of antioxidants, other corrosion and rust inhibitors, metal deactivators, extreme pressure or anti-wear additives, complexing agents, precipitation inhibitors, biocides, buffering agents and anti foams. 
     
     
       17. A composition according to claim 1 wherein the system is completely aqueous and the system also contains one or more further corrosion inhibitors, dispersing and/or threshold agents, precipitating agents, oxygen scavengers, sequestering agents; antifoaming agents; and biocides. 
     
     
       18. A composition according to claim 1 wherein the system is partly aqueous and the system also contains one or more further corrosion inhibitors or extreme-pressure additives. 
     
     
       19. A method of protecting a metal surface against corrosion, which comprises applying a composition according to claim 1 to said metal surface.